An incubator capable of providing a controlled environment for a weak or sickly neonate like an immature infant has generally a conditioned-air supplying device whose temperature, humidity, oxygen content and so forth have been conditioned. In order to purify, with a filter, both the air of a space where an incubator is set, for example, a ward of an obstetrics and gynecology hospital (hereinafter described as "the outside air") and, if necessary, the oxygen supplied from an oxygen bomb (hereinafter described as "the supplied oxygen") and in order to supply them to the hood of the incubator, the conditioned-air supplying device of this type generally has a filter mounting apparatus of mounting the filter on the base of the incubator.
Shown in FIGS. 15-17 is one example of conventional fluid flow controlling device of the incubator (hereinafter described as "the first former example"). In FIGS. 15-17, the fluid flow controlling device is in a state of being incorporated in the filter mounting apparatus of an incubator, so that the filter mounting apparatus as well as the fluid flow controlling device will be explained on reference to FIGS. 15-17.
In the filter mounting apparatus shown in FIGS. 15-17, the bottom plate portion 4 of a box-like filter accommodating case 7 is fixed to the back wall portion 3 of a base 1 with a pair of right and left stud bolts 9, 11. On the upper side of the base 1, a neonate's support (not shown) is provided and, in the filter accommodating case 7, a stepped portion 6 of substantially rectangular shape is formed along the outer periphery of the bottom plate portion 4. Further, a small gas passage aperture 5 is provided in the bottom plate portion 4. The base 1 has a transparent hood (not shown) that covers the neonate lying on the neonate receptacle which is disposed in the upper portion of the base 1. The base 1 is generally put on a table (not shown), on which the incubator is set. In the back wall portion 3 of the base 1, a gas passage aperture 8 is provided in correspondence with the gas passage aperture 5 of the filter accommodating case 7.
As shown in FIGS. 15 and 16, the stud bolts 9, 11 project from the back wall portion 3 of the base 1 into the filter accommodating case 7 and are inserted into a pair of right and left apertures 15, 17 of an air filter 13, which is made of nonwoven pad or the like, so that the air filter 13 is accommodated in the filter accommodating case 7 in such a state that its substantially rectangular outer periphery abuts against the stepped portion 6. The side portion of a vessel-like filter cover 19 is fitted into the side wall of the filter accommodating case 7 so that the outer periphery of the air filter 13 is pressed against the stepped portion 6 by a pressing portion 19a formed by bending the distal end of the filter cover 19 and arranged in opposed relation to the stepped portion 6.
As shown in FIG. 16, rotatably mounted on the filter cover 19 is a pair of right and left clamp devices 23, 25, in each distal end portion of which box nut portion 23a, 25a is formed. When the pair of clamp devices 23, 25 are rotated by hand, each box nut portion 23a, 25a is screwed on the distal end of each corresponding stud bolt 9, 11. Thus, the filter cover 19 fitted into and fixed to the filter accommodating case 7 against the elastic force of the air filter 13 presses the outer periphery of the air filter 13 with its pressing portion 19a against the stepped portion 6 of the bottom plate portion 4 of the filter accommodating case 7, so that the air filter 13 is fixed to the stepped portion 6. As a result of the foregoing, a pre-filter chamber 29 is formed between the air filter 13 and the front plate portion 19b of the filter cover 19 and a post-filter chamber 30 is formed between the air filter 13 and the bottom plate portion 4 of the filter accommodating case 7.
Provided on the filter cover 19 is a flow controlling mechanism 31, whereby the outside air and the supplied oxygen are led into the pre-filter chamber 29 through a gas inlet 27 formed in the front plate portion 19b of the filter cover 19. As shown in FIGS. 17A and 17B, the flow controlling device 31 has a blockish body 35 fixed to the front plate portion 19b of the filter cover 19. The blockish body 35 has an air inlet 33 provided in correspondence with the gas inlet 27 formed in the front plate portion 19b of the filter cover 19. Further, fixedly mounted in the blockish body 35 is a connecting pipe 39, to which the distal end of an oxygen supplying pipe 37 is connected. The pipe 37 leads oxygen from an oxygen bomb (not shown). It is noted that the oxygen supplying pipe 37 communicates with the air inlet 33 through a connecting pipe 39. An air valve body 41 is mounted on the blockish body 35 through its shaft portion 41a so as to be movable back and forth, and urged toward its retreated position due to the force of a coiled spring 43, so that the air inlet 33 is to be closed in the front end portion thereof by the air valve body 41. The front end portion serves as a valve seat.
At ordinary time (including the time not in use), a marker panel 45 is mounted on the flow controlling device 31. The marker panel 45 is substantially flat and has a slotted portion 45a extending from its lower end. Further, a short horizontal plate portion 45b with an engaging aperture 47 projects from the center of the back surface of the marker panel 45.
When the filter mounting apparatus shown in FIGS. 15-17, in which the flow controlling device 31 is incorporated, is used at ordinary time, it should be performed beforehand as shown in FIG. 17A to insert the lower end of the marker panel 45 between the air valve body 41 and the blockish body 35 of the flow controlling device 31; to fit the shaft 41a of the air valve body 41 into the slotted portion 45a; and to fit a projection 35a protruding from the blockish body 35 into the engaging aperture 47. It is noted that at ordinary time, the air valve body 41 is in its advanced position and is apart from the front end of the air inlet 33, so that the air inlet 33 serves to communicate the pre-filter chamber 29 with the outside.
Therefore, when the air circulating fan (not shown) of the conditioned-air supplying device disposed within the base 1 is driven, the outside air is led into the pre-filter chamber 29 through the air inlet 33 and the gas inlet 27. If necessary, the valve of the oxygen bomb (not shown) will be opened in a suitable degree. In that event, the supplied oxygen from the oxygen bomb is led into the air inlet 33 through the oxygen supplying pipe 37 and the connecting pipe 39 and, then, led into the pre-filter chamber 29 together with the above outside air. As the result, the air suitably enriched with the supplied oxygen whose quantity depends upon the opening rate of the valve flows from the pre-filter chamber 29 to the air circulating fan (not shown) through the air filter 13, the post-filter chamber 30 and the gas passage apertures 5, 8. Thus, the air is purified due to the air filter 13.
However, in a state of ordinary use shown in FIG. 17A, if the valve of the oxygen bomb is fully opened to supply a flow of 15 lit/min for example, the air also flows into the pre-filter chamber 29 through the air inlet 33 and the gas inlet 27, so that it is difficult to get high concentration of oxygen in the air (that is, the air enriched with the supplied oxygen) taken in the hood of the incubator and, in the example shown in FIG. 17A, the concentration is about 40% at the utmost if the flow of the supplied oxygen is 15 lit/min.
In the meantime, if the neonate lying on the neonate's receptacle is in an abnormal state, it will be required to supply much oxygen to the hood of the incubator. In such case, the valve of the oxygen bomb is fully opened and the marker panel 45 is disengaged from the blockish body 35 of the flow controlling device 31. As the result, the air valve body 41 retreats due to the force of the coiled spring 43, so that the front portion of the air inlet 33 is blocked up as shown in FIG. 17B. Thus, the outside air is not led into the pre-filter chamber 29 and only the supplied oxygen is led into the pre-filter chamber 29.
However, in the first former example, shown in FIGS. 15-17, of the flow controlling device 31, when the state of ordinary use shown in FIG. 17A is changed to the state of extraordinary use shown in FIG. 17B, in which the neonate is in the abnormal state, it is required that not only the valve of the oxygen bomb is fully opened, but also the marker panel 45 is disengaged from the blockish body 35 of the flow controlling device 31. On the contrary, when the state of extraordinary use is changed to the state of ordinary use, it is required that not only the valve of the oxygen bomb is closed by a certain degree or completely, but also the marker panel 45 is engaged with the the blockish body 35 of the device 31. Further, when the oxygen bomb empties in the state of extraordinary use, in which the neonate is in the abnormal state, not only the supplied oxygen but also the outside air are not led into the pre-filter chamber 29 because of the blockade of the air inlet 33. In addition, broken-line A shown in FIG. 19, which represents the relationship, in the state of extraordinary use, between the oxygen flow from the oxygen bomb and the oxygen concentration in the air (that is, the air enriched with the supplied oxygen) within the hood of the incubator, has steep gradient at its initial stage because the air inlet 33 has been blocked up, so that the fine control of the oxygen concentration is difficult.
Shown in FIG. 18 is another example of the conventional fluid flow controlling devices of the incubator previously stated (hereinafter described as "second former example"). In FIG. 18, the fluid flow controlling device is in a state of being located adjacent to the filter mounting apparatus of the incubator, so that the filter mounting apparatus as well as the fluid flow controlling device will be explained on reference to FIGS. 18A and 18B. Further, the same reference numerals will be used for the members common between the first former example shown in FIGS. 15-17 and the second former example shown in FIGS. 18A and 18B, and the explanation for each common member will be omitted.
In the fluid flow controlling device 31 shown in FIGS. 18A and 18B, a connecting pipe 39, to which the distal end of the oxygen supplying pipe 37 for supplying the supplied oxygen from the oxygen bomb (not shown) is connected, is fixed to the back wall portion 3 of the base 1 and projects outwards therefrom. On the upper side of the base 1, a neonate's support (not shown) is provided. A bellowslike conduit 51 made of elastic material such as silicon rubber and having a front plate portion 51a fixed to the back wall portion 3 is arranged in a first inner space 52 formed on the inside of the the back wall portion 3 so as to be in alignment with the connecting pipe 39. Further, provided in the base 1 is a partition board 53 extending substantially in parallel with the back wall portion 3 and, in the partition board 53, a gas inlet 27 formed in the shape of a circular truncated cone is provided so as to be substantially in alignment with the connecting pipe 39. In the rear plate portion 51b of the bellowslike conduit 51, a projection 51c that has substantially the same shape as the gas inlet 27 (that is, the shape of the circular truncated cone) is formed integrally with the rear plate portion 51b so as to be substantially in alignment with the connecting pipe 39, and an oxygen outlet 55 is formed through the central portion of the projection 51c. Further, a coiled spring 43 lies between the rear plate portion 51b of the bellowslike conduit 51 and the partition board 53 so as to be substantially in alignment with the connecting pipe 39.
In the second inner space 54 formed on the inside of the partition board 53 of the base 1, an air filter 13 is arranged substantially in parallel with the partition board 53 and, between the air filter 13 and the partition board 29, a pre-filter chamber 29 is formed. Further, on the inside of the air filter 13, a post-filter chamber 30 is formed.
When the fluid flow controlling device 31 and the filter mounting apparatus shown in FIGS. 18A and 18B are to be used in the state of ordinary use, the air circulating fan (not shown) of the conditioned-air supplying device should be driven under the condition illustrated in FIG. 18A. As the result, the air led into the first inner space 52 of the base 1 through an outside air inlet (not shown) formed in the back wall portion 3 of the base 1 is supplied to the pre-filter chamber 29 via the outside of the bellows conduit 51 and through the gas inlet 27.
If the valve of the oxygen bomb (not shown) is opened in a necessary degree, the supplied oxygen from the oxygen bomb is led into the bellowslike conduit 51 through the oxygen supplying pipe 37 and the connecting pipe 39 and successively led into the pre-filter chamber 29 through the oxygen outlet 55, via a part of the first inner space 52 and through the gas inlet 27. In that event, the rear plate portion 51b of the bellowslike conduit 51 moves rearwards (toward the left in FIG. 18A) in correspondence with the degree of the valve opening, due to the pressure of the supplied oxygen led into the inside of the bellowslike conduit 51, and against the force of the coiled spring 43, so that the bellowslike conduit 51 extends and the projection 51c approaches the gas inlet 27. Thus, the flow of the outside air passing through the outside of the bellowslike conduit 51 and led into the pre-filter chamber 29 is reduced in correspondence with the degree of the approximation of the projection 51c to the gas inlet 27.
As a result of the foregoing, the air within the pre-filter chamber 29 and enriched with the suitable quantity of the supplied oxygen, which depends upon the degree of the valve opening, moves toward the air circulating fan (not shown) through the air filter 13 and the post-filter chamber 30, so that the air is purified by the air filter 13.
In the meantime, when the fluid flow controlling device 31 and the filter mounting apparatus are used in the state of extraordinary use, in which the neonate is in the abnormal state, the valve of the oxygen bomb is fully opened, so that a large quantity of the supplied oxygen is led into the inside of the bellowslike conduit 51 and, due to the pressure of the supplied oxygen, the rear plate portion 51b of the bellowslike conduit 51 moves rearwards against the force of the coiled spring 43 until the projection 51c is fitted into the gas inlet 27 and the two touch completely. Thus, the flow of the outside air is intercepted between the outside of the bellowslike conduit 51 and the pre-filter chamber 29. In other words, the air is not led into the pre-filter chamber 29 via the outside of the bellowslike conduit 51 and only the supplied oxygen is led into the pre-filter chamber 29.
However, in the second former example 31 of conventional fluid flow controlling devices shown in FIGS. 18a and 18B, the bellowslike conduit 51 of elastic material such as silicon rubber is a requisite member and it must expand and contract in correspondence with the flow of the supplied oxygen. However, the correspondence often breaks down because the expansion and contraction characteristic of the bellowslike conduit 51 varies with every product and the conduit 51 does not always act smoothly. Further, the bellowslike conduit 51 is apt to be damaged for the duration of the long-term use. In addition, the bellowslike conduit 51 must expand against the force of the coiled spring 43 as the flow of the supplied oxygen increases, but the inclination of the expansion of the bellowslike conduit 51 to the flow of the supplied oxygen is gentle, so that broken-line B shown in FIG. 19, which represents the relationship between the flow of the supplied oxygen and the oxygen concentration in the air within the hood to the incubator, has a gentle gradient substantially over its whole range. Further, a part of the supplied oxygen within the bellowslike conduit 51 is apt not to flow into the gas inlet 27 via the oxygen outlet 55 but to leak through to the outside of the bellowslike conduit 51 and, as the result, the supplied oxygen is apt to be wasted.